Fiber for artificial hair and process for producing the same

ABSTRACT

A fiber having unique gloss of appearance (flickering gloss) with light diffusibility, while maintaining natural feeling of gloss necessary as fiber for hair, is provided. The present invention may be attained by an artificial fiber for hair obtained from an acrylic based synthetic fiber having a single fiber size of 20 dtex to 80 dtex, the fiber having a maximum reflectance to a white light of 15% to 36% in case of a fiber having less than 21 of L value, or of 36% to 70% in case of a fiber having not less than 21 of L value, and having an optical diffusion coefficient of not less than 0.25.

This is a 371 national phase application of PCT/JP2003/008943 filled 14Jul. 2003, claiming priority to Japanese Application No. 2002-222387filed 31 Jul. 2002, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to a fiber for artificial hair, such aswigs, hairpieces, braids, extension hair, headdress for dolls, etc.Furthermore, it specifically relates to a novel fiber for artificialhair exhibiting reflective characteristics accompanied by lightdiffusibility and having unique appearance-gloss, and also to a methodfor manufacturing the same.

BACKGROUND ART

Acrylic based fibers, vinyl chloride based fibers, vinylidene chloridebased fibers, polyester fibers, nylon fibers, polypropylene fibers, etc.are known well as fibers for artificial hair. These fibers are appliedin fields, such as wigs, hair accessories, weavings, braids, extensionhair, and hair for dolls, and various investigation has been performeduntil today in order to provide characteristics necessary as fibers forhair, such as improvement in touch and gloss, combing ability, curlretentivity, stylability (fiber performance enabling various styles inwig application).

Especially in gloss, since these synthetic fibers have very smooth fibersurface, in general, they are not suitable for a fiber for hair withoutspecific treatment in respect of appearance, touch, etc. Therefore,there have been made efforts for exhibiting gloss similar to human hair,such as: methods by addition of dulling agent currently disclosed inJapanese Patent Publication No. No. 56-44164, Japanese Patent Laid-OpenNo. 56-309, Japanese Patent Laid-Open No. 56-311, etc., and methods bysurface-roughing currently disclosed in Japanese Patent Laid-Open No.61-245301, Japanese Patent Laid-Open No. 63-12716, Japanese PatentLaid-Open No. 05-140807, Japanese Patent Laid-Open No. 5-140817, etc.,thereby enabling broad use for hair article.

However, in recent years, greater importance is being placed onfashionability also in headdress field, and as a result fibers havingspecific brightness and higher-class feeling are strongly desired to bemarketed. Although conventional fibers exhibit natural feeling of glossby the above-mentioned addition of dulling agent or by surfacetreatment, minute uneven shape on a surface of the fibers gives onlymonotonous appearance-gloss, and cannot fully satisfy requests in marketin the present circumstances.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a fiber that has uniquegloss of appearance (flickering gloss) with light diffusibility whilemaintaining natural gloss necessary for fibers for hair.

As a result of wholehearted investigation performed by the presentinventors in order to develop a fiber having unique appearance-glosswhile satisfying requests in market, application of a specific knot-likeunevenness shape on a fiber surface successfully enabled development ofa fiber with unique gloss of appearance having light diffusibility, thatis, flickering gloss, and furthermore, it was also found out that theunique targeted gloss of appearance can be expressed using a reflectanceto a white light, and an optical diffusion coefficient, and in additionan appropriate range thereof was also found out, leading to completionof the present invention.

That is, the present invention relates to an artificial fiber for hairobtained from an acrylic based synthetic fiber having a single fibersize of 20 dtex to 80 dtex, the artificial fiber comprising: areflectance to a white light within a range of either of following (1)or (2); and an optical diffusion coefficient of a fiber of not less than0.25.

-   (1) A reflectance of 15% to 36% in case of a fiber with an L value    of less than 21 in Hunter's Lab.-   (2) A reflectance of 36% to 70% in case of a fiber with an L value    of not less than 21 in Hunter's Lab.

And furthermore, as a preferable embodiment, the present inventionrelates to an artificial fiber for hair having a knot-like unevenness ona fiber surface, an average difference of height between a projectedarea and a depressed area of 5 micrometers to 15 micrometers, and adistance between peaks of adjacent projected areas in a range of 0.05 mmto 0.5 mm.

Moreover, the present invention relates to an artificial fiber for hairobtained from a resin composition having, as a principal component, apolymer consisting of acrylonitrile 30% to 85% by weight, a halogencontaining monomer 14% to 69% by weight, and a hydrophilic olefin basedmonomer having a sulfonic acid group 1.0% to 3.0% by weight, The presentinvention also relates to a method for manufacturing an artificial fiberfor hair, using a spinning solution prepared using an organic solvent soas to give a viscosity of 3 Pa-sec to 10 Pa-sec in wet spinning of theresin composition, using a nozzle having an L/W value of a projection of0.5 to 2.0, and a cross section shape with 4 to 8 projections connectedin a radial direction, performing wet spinning under a condition of anozzle draft coefficient of 0.8 to 1.3, and then drying a fiber obtainedunder a wet and heated atmosphere with a dry heating temperature of notless than 120 degrees C. and with a wet-bulb temperature of not lessthan 70 degrees C. after washing with water.

Hereinafter, detailed description of the present invention will begiven. An artificial fiber for hair of the present invention is anacrylic based synthetic fiber obtained from an acrylic based copolymerincluding acrylonitrile, and preferably is an acrylic based syntheticfiber obtained from a resin composition having, as a principalcomponent, a polymer consisting of acrylonitrile 30% to 85% by weight, ahalogen containing monomer 14% to 69% by weight, and a hydrophilicolefin based monomer having a sulfonic acid group 1.0% to 3.0% byweight.

The halogen containing monomer as used herein includes, but not limitedto, vinyl chloride, vinylidene chloride, vinyl bromide, vinylidenebromide, etc. Vinylidene chloride and vinyl chloride are preferable inrespect of easy availability among them. Moreover, other mono-olefinbased monomers copolymerizable with them may also be used, if needed, bya grade not disturbing the present invention.

As other mono-olefin based monomers, for example, acrylic acid,methacrylic acid and esters thereof, acrylamide, vinyl acetate, etc. maybe mentioned, and among them methyl acrylate and methyl methacrylate arepreferable in view of excellent reactivity and improvement in dyeaffinity. Less than 14% by weight of the halogen containing monomer inthe acrylic based copolymer may not easily give soft and animalhairs-like touch, and an amount exceeding 69% by weight reduces heatresistance and shows an undesirable tendency for the fibers to be easilywelded together during a manufacturing process.

Moreover, as hydrophilic olefin based monomers including a sulfonic acidgroup, for example, but not limited to, includes sodiumpara-styrenesulfonate, sodium methallyl sulfonate, sodiumisoprenesulfonate (2-methyl-1,3-butadiene-1-sodiumsulfonate), sodium2-acrylamido-2-methyl propanesulfonate(acrylamide-t-butyl-sodiumsulfonate), para-styrene sulfonate, methallylsulfonate, isoprene sulfonate (2-methyl-1,3-butadiene-1-sulfonate),2-acrylamido-2-methyl propane sulfonate (acrylamido-t-butyl-sulfonate)etc.

Moreover, from a viewpoint of excellent reactivity and easyavailability, sodium para-styrenesulfonate, sodium methallylsulfonate orsodium isoprene sulfonate, and 2-acrylamido-2-methyl propane sulfonate(acrylamido-t-butyl-sulfonate) are preferable. In order to formpredetermined voids in a coagulation bath, this hydrophilic olefin basedmonomer including a sulfonic acid group is especially necessary, and acontent thereof is preferably in a range of 1.0% to 3.0% by weight in anacrylic based copolymer. A content outside this range cannot developvoids having a target size in a coagulation bath, resulting indifficulty of providing a fiber having target unevenness by amanufacturing method of the present invention, except when the targetunique appearance characteristics and unevenness on a surface of thefiber are given without forming voids.

Reflectance to a white light as used in the present invention is anindex designating a gloss value (luster) of a fiber, which is obtainedas a maximum reflectance as follows. Eleven fibers are optionally chosenfrom a fiber bundle, a reflected light distribution from the fibers forincident light with an angle of incidence of 30 degrees is measuredusing Murakami Color Research Laboratory glossimeter (GONIOPHOTOMETERGP-200 type), and a halogen lamp (white) as a light source. FIG. 1shows an example of a reflected light distribution. In FIG. 1, referencefigure (a) gives a value of a maximum reflectance.

Natural feeling of gloss as artificial hair may be obtained by adjustinga reflectance to a white light of an artificial fiber for hair of thepresent invention to a range of 15% to 36%, in case of a fiber with an Lvalue in Hunter's Lab of less than 21, and by adjusting to a range of36% to 70% in case of a fiber with an L value in Hunter's Lab not lessthan 21.

An L value of Hunter's Lab here represents a value measured by a methodaccording to JIS Z 8722, and an L value represents lightness. A fiberhaving an L value of less than 21, in general, is equivalent to a deepcolor fiber, and a fiber having a value L of not less than 21 isequivalent to a fiber of medium color to light color. When a fiberequivalent to each of the L values has a reflectance lower than therange, the fiber will become a fiber similar to kemp, giving dull huewith low commercial value. On the other hand, a reflectance out of therange may give plastic gloss, and the fiber then is not suitable for afiber for hair.

An optical diffusion coefficient as used herein represents dispersionproperty of a reflected light in the present invention. A half valuebreadth (b) is obtained, which is a width of distribution of a value ofa half of maximum reflectance (a) from the reflected light distribution(FIG. 1) obtained on a same measurement conditions as of thereflectance. The value is calculated by a following equation.Optical diffusion coefficient (D)=b/aWhere,

-   a: Maximum reflectance (%)-   b: Half value breadth (degree).

This optical diffusion coefficient has a good correlation with aflickering gloss given by a visually observed fiber. The largerdiffusion coefficient may give larger flicker degree, and an article offinal stage, such as wigs, may exhibit unique gloss of appearance notfound in conventional products, resulting in a high-grade article.According to inventors' teaching, in order to exhibit flickering glossfor visual observation, a diffusion coefficient of not less than 0.25 isnecessary, and a diffusion coefficient of less than 0.25 gave only alittle flickering gloss, and gave appearance of article practicallysimilar to conventional article.

When an artificial fiber for hair of the present invention has, on afiber surface thereof, a knot-like unevenness, 5 micrometers to 15micrometers of a difference of average height between a projected areaand a depressed area, and a distance between peaks of adjacent projectedareas in a range of 0.05 mm to 0.5 mm, numerical ranges of a reflectanceto a white light and an optical diffusion coefficient may preferably besatisfied.

Furthermore, a difference of average height between a projected area anda depressed area is preferably 6 micrometers to 12 micrometers, and adistance between peaks of adjacent projected areas is 0.06 mm to 0.40mm. Here, an expression “fiber surface has a knot-like unevenness”designates a shape as schematically shown, for example in FIG. 2. Adifference of average height between a projected area and a depressedarea at this time may be obtained by measuring a length of a thickerportion of a fiber (H1), and a finer portion (H2) in FIG. 2, andcalculated with a following equation.A difference of average height between a projected area and a depressedarea (H)=(H1−H2)×½Where,

-   H1: a length of thicker portion-   H2: a length of finer portion.

Moreover, as shown in FIG. 2, a distance between peaks of adjacentprojected areas may also be obtained by measuring a pitch between peaksof adjacent projected areas.

The present inventors found out that a fiber having unique gloss ofappearance with light diffusibility, i.e., flickering gloss, might beobtained by applying uneven shape in this particular range to a fibersurface.

When a difference of average height between a projected area and adepressed area is smaller than 5 micrometers, or when a distance betweenpeaks of adjacent projected areas is larger than 0.5 mm, other designideas are necessary in order to obtain a target fiber having not lessthan 0.25 of optical diffusion coefficients. Although a difference ofaverage height between a projected area and a depressed area exceeding15 micrometers increases optical diffusion coefficient, itdisadvantageously gives excessive rough touch for a fiber to worsenfeeling, except when gloss of appearance is realized by other designideas.

A single fiber size of an artificial fiber for hair of the presentinvention is 20 dtex to 80 dtex. A size of a fiber of less than 20 dtexexhibits touch with excessive softness and without resilience, resultingin unsuitable fiber for a headdress product. On the other hand, since asize of a fiber exceeding 80 dtex gives rigid touch to a fiber andsignificantly reduces touch of the fiber, it is important that the fiberpreferably has an appropriate size of 30 dtex to 70 dtex.

A description about a method for manufacturing an artificial fiber forhair of the present invention will hereinafter be given. Although amethod of manufacturing an artificial fiber for hair of the presentinvention is not especially limited, for example, the fiber can bemanufactured by following methods.

Any polymerization methods for vinyl based monomers usually known may beused as copolymerization methods for acrylic based polymers used for anartificial fiber for hair of the present invention, and for example, asuspension polymerization method, a solution polymerization method, anemulsion polymerization method, etc. may be mentioned.

Next, a resin composition having an acrylic based polymer as a principalcomponent is dissolved in an organic solvent to prepare a spinningsolution. The organic solvents used here for the spinning solution arenot especially limited, as long as they dissolve the resin composition,and for example, dimethylformamide, dimethylacetamide,dimethylsulfoxide, acetone, acetonitrile, etc. may be mentioned.Moreover, it is also possible to add to the spinning solution mattingagents, coloring stabilizers, flame resistant agents, light stabilizers,rust preventives, antistatic agents, antibacteria agents, etc. ifneeded.

A viscosity of the spinning solution is preferably in a range of 3Pa-sec to 10 Pa-sec, and more preferably in a range of 4 Pa-sec to 8Pa-sec. This preferable range of the viscosity of the spinning solutionis a condition necessary for formation of specific voids in acoagulation bath mentioned later. A viscosity of the spinning solutionof less than 3 Pa-sec gives excessively large voids formed in thecoagulation bath, and worsens recoverability of lost transparency in adrying process, disadvantageously resulting in a fiber with kemp tonehaving dull hue.

On the other hand, a viscosity exceeding 10 Pa-sec of the spinningsolution makes the fiber denser in the coagulation bath, cannot formvoids having a target size to provide a fiber surface having a smalldegree of uneven shape, and as a result only a fiber with small opticaldiffusion coefficient can be obtained.

A spinning solution prepared in this way is then spun by a usual wetspinning method, and the spinning solution is preferably spun using, asa nozzle to be used, a nozzle having a cross section shape with an L/Wvalue for projections of 0.5 to 2.0, and having 4 to 8 projectionsconnected in radial directions.

The nozzle is used in order to obtain a yarn having voids with a size ofabout 5 micrometers to 30 micrometers in the coagulation bath, and thevoids are believed to be crushed in a next drying process, thuspresenting a knot-like unevenness on a fiber surface.

A cross section shape as used herein that has projections connected inradial directions is a cross section shape as shown, for example in (a)to (c) of FIG. 3, and an L/W value for a projection is represented witha ratio (L/W) of a length (L) and a width (W) of the projection as shownin FIG. 4. Use of the nozzle with the shape of the range enablesdevelopment of the target voids in the coagulation bath. An L/W valueless than 0.5 makes a diameter of the voids smaller, and an L/W valueexceeding 2.0 excessively enlarges a diameter of the voids, leading to aproblem of difficulty in recovery of lost transparency.

Moreover, a number of projections of the nozzle is preferably 4 to 8,and more preferably 5 to 7. A number smaller than 4 fails to allowdevelopment of the voids, but a number exceeding 8 reduces a slit widthof the nozzle, causing an undesirable problem of poor spinnability.

Furthermore, in spinning of the spinning solution through the nozzle, anozzle draft coefficient may preferably be set to 0.8 to 1.3. The nozzledraft coefficient may be calculated by a equation described later. Anozzle draft coefficient smaller than 0.8 fails to develop voids havinga target size, and a nozzle draft coefficient exceeding 1.3 easilycauses yarn breakage etc.Nozzle draft coefficient=V0/V1

-   V0: Linear velocity at a nozzle outlet-   V1: Taking up linear velocity

After formation of specific voids in a coagulation bath by theabove-mentioned method, water-washing with warm water etc., and drawingare carried out, and subsequently drying under specific conditions isperformed. Specifically, drying is performed under an atmosphere withwet hot wind of a dry heating temperature of not less than 120 degreesC., and a wet-bulb temperature of not less than 70 degrees C.

It is difficult for usual drying conditions to recover losttransparency, since large voids are formed in a stage of solidificationof a yarn, and therefore, it is necessary to use the above-mentioneddrying conditions. Especially a wet-bulb temperature is important and itis preferably not less than 70 degrees C., and more preferably no lessthan 80 degrees C.

A wet-bulb temperature as used herein is a temperature measured usingwhat is called a psychrometer having a temperature sensor wrapped with awet cloth in a thermometer. A higher wet-bulb temperature means moremoisture contents under a drying atmosphere, and therefore much moreheat conduction to a fiber may be realized as compared with usual dryhot wind, probably causing easy crushing of the voids.

A dry heating temperature lower than 120 degrees C. or a wet-bulbtemperature lower than 70 degrees C. cannot provide satisfactorycrushing of the voids, and as a result, only a fiber having small degreeof unevenness and small optical diffusion coefficient is obtained.

The manufacturing method of the present invention is characterized byproviding a fiber surface with uneven shape due to crushing underspecific drying conditions large voids formed in solidification. Theabove-mentioned viscosity of the spinning solution, a nozzle with aparticular shape, a nozzle draft coefficient, and drying conditions areespecially important, and by satisfying these manufacturing conditions,a target artificial fiber for hair can be obtained. However, it is notlimited to obtain an artificial fiber for hair of the present inventionby methods other than manufacturing conditions of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a maximum reflectance and a half value breadthbased on an example of a distribution of reflected light of an incidentwhite light to a fiber;

FIG. 2 is a schematical diagram (a section in a lengthwise direction ofa fiber) of an uneven shape of an artificial fiber for hair of thepresent invention;

FIG. 3 is an example of a cross section shape of a nozzle used in amanufacturing method of the present invention; and

FIG. 4 is a diagram of a value L and a value W for projections of anozzle used in a manufacturing method of the present invention.

BEST MODE FOR CARRYING-OUT OF THE INVENTION

Although, detailed description of the present invention will,hereinafter, be given based on Examples, the present invention is notlimited to these Examples at all. Definitions of measuring methods etc.will be described in advance of description of Examples.

(Maximum Reflectance)

Eleven numbers of fibers were optionally chosen from a fiber bundle, andthe fibers were measured for a reflected light distribution from thefibers with a light at 30 degrees of angle of incidence to obtain amaximum reflectance, using a glossimeter by Murakami Color ResearchLaboratory (GONIOPHOTO METER GP-200 type) with a halogen lamp (12 V, 50W) as a light source, at a voltage of −760 V.

(Optical Diffusion Coefficient)

A half value breadth designating a distribution width of a value of ahalf of a maximum reflectance was determined, from a reflected lightdistribution obtained by the method. Optical diffusion coefficient wascalculated using a following equation. (Refer to FIG. 1)Optical (diffusion coefficient D)=b/aWhere,

-   a: Reflectance (%), b: Half value breadth (degree).    (L Value)

Using a colorimetric photometer made by [Nippon Denshoku Co., Ltd.] (Σ90), and a whiteness standard plate attached to the photometer, a bundleof fibers of a length of 20 cm and gross size 900,000 dtex was placedsideways, on a reflective sample stand with 30 φ, and measurement wasperformed 3 times by a method according to JIS Z 8722. An average (Lvalue) was calculated.

(Fiber Surface Unevenness Measurement)

A side surface of the a was observed by a magnification of 100 timesusing an optical microscope made by Olympus Corporation, and as shown insecond figure, a thicker portion and a finer portion of the fiber weremeasured for H1 and H2, and H was calculated by a following equation. Inaddition, measurement was performed with n=30 and an average wascalculated.Difference of average height of a projected area and a depressed area(H)=(H1−H2)×½

-   H1: length of thicker portion-   H2: length of finer portion

Moreover, a distance between peaks of adjacent projected areas was alsomeasured for 30 portions, as shown in FIG. 2, and an average wascalculated.

(Spinning Solution Viscosity)

A solution was measured for a viscosity at 40 degrees C. using a B-typeviscometer manufactured by Shibaura Systems Co., Ltd.

(Gloss of Appearance Evaluation)

Using a fiber bundle of gross size900,000 dtex, a flicker degree ofgloss was sensuously evaluated by five persons based on visual feeling,and evaluation was made with three steps of following criteria for glossof appearance.

-   ◯: Flickering gloss with unique appearance observed-   Δ: A small degree of insufficient flickering gloss observed-   X : Flickering gloss hardly observed

EXAMPLE 1

An acrylic based polymer consisting of acrylonitrile (AN) 52% by weight,vinylidene chloride (VD) 46.5% by weight, and sodium styrene sulfonate(3S) 1.5% by weight was dissolved in acetone, to obtain a spinningsolution with a viscosity of 5 Pa-sec by adjusting a resin concentrationto 26% by weight.

This spinning solution was extruded in a coagulation bath ofacetone/water having 36% by weight of acetone concentration at 20 degreeC., using a nozzle [FIG. 3( b)] that has a cross section shape havingsix projections connected in radial directions with 1.4 of an L/W value,and that has a pore size of 0.3 φ and a number of holes of 50, with anozzle draft coefficient of 0.9. Subsequently, a yarn obtained wasintroduced into a water-washing bath at 50 to 60 degrees C., and a 1.9times of preliminary drawing was given with concurrent washing by water.

After 2.0 times of hot drawing, lost transparency was recovered bydrying under an atmosphere of wet heated wind of a dry heatingtemperature of 125 degree C., and a wet-bulb temperature of 80 degreeC., 10% of relaxation heat treatment was performed under a 160-degree C.dry heating atmosphere.

The obtained fiber was a white fiber having a single fiber size of 50dtex, and an L value of 85, and it had an uneven shape on a fibersurface thereof, a difference of average height between a projected areaand a depressed area of 8 micrometers, and an average distance betweenpeaks of adjacent projected areas of 0.25 mm. Moreover, a maximumreflectance to a white light (halogen lamp) gave 55%, and an opticaldiffusion coefficient 0.32.

EXAMPLE 2

After a similar fiber as in Example 1 was manufactured, a fiber withbrown hue was obtained by a piece dyeing processing using a followingmethod.

In the piece dyeing processing method, boiling of 1 hour at an ordinarypressure was performed at a bath ratio of 1:25, using cationic dyes(Maxilon Yellow 2RL 0.36% omf, Maxilon Red GRL 0.06% omf, Maxilon BlueGRL 0.18% omf, manufactured by Ciba-Geigy Corp.), as an auxiliary agent,acetic acid, sodium acetate, and anionic dispersing agent 2% omf(Levenol WX: made by Kao Corp.), and an accelerating agent 0.4% omf(sodium lauryl sulfate), and then water-washing and drying treatmentwere performed. A fiber after dyed was a brown fiber having an L valueof 31, and it had 36% of maximum reflectance and 0.40 of light diffusioncoefficient.

EXAMPLE 3

After a similar fiber as in Example 1 was manufactured, a fiber withblack hue was obtained by a piece dyeing processing using a followingmethod.

In the piece dyeing processing method, boiling of 1 hour at an ordinarypressure was performed at a bath ratio of 1:25, using cationic dyes(Maxilon Yellow 2RL 0.78% omf, Maxilon Red GRL 0.24% omf, Maxilon BlueGRL 0.58% omf, manufactured by Ciba-Geigy Corp.), as an auxiliary agent,acetic acid, sodium acetate, and anionic dispersing agent 2% omf(Levenol WX: made by Kao Corp.), and an accelerating agent 0.6% omf(sodium lauryl sulfate), and then water-washing and drying treatmentwere performed.

The fiber after dyed was a black fiber having an L value of 17, and ithad 24% of maximum reflectance, and 0.45 optical diffusion coefficient.

EXAMPLE 4

An acrylic based polymer consisting of acrylonitrile 56% by weight,vinylidene chloride 42% by weight, and sodium styrene sulfonate 2% byweight was dissolved in DMF (N,N-dimethylformamide), to obtain aspinning solution with a viscosity of 8 Pa-sec by adjusting a resinconcentration to 25% by weight. Subsequently, using a same nozzle as inExample 1, at a nozzle draft coefficient of 0.9, the spinning solutionwas extruded in an aqueous solution with 50% by weight of DMF.Subsequently, the fiber obtained was introduced into a water-washingbath at 80 degrees C., and a 2.0 times of preliminary drawing was givenwith concurrent washing by water.

After 2.0 times of hot drawing, lost transparency was recovered bydrying under an atmosphere of wet heated wind of a dry heatingtemperature of 140 degree C., and a wet-bulb temperature of 80 degreeC., 8% of relaxation heat treatment was performed under a 160-degree C.dry heating atmosphere. Subsequently, the fiber was colored by a similarmethod as in Example 2, and a brown fiber having a single fiber size of50 dtex and an L value of 35 was obtained.

The obtained fiber had uneven shape, and moreover a difference ofaverage height between the projected area and the depressed area of 7micrometers, and an average distance between peaks of adjacent projectedareas of 0.27 mm on a surface thereof. Moreover, the fiber had a 37% ofmaximum reflectance to white light and an optical diffusion coefficientof 0.36.

COMPARATIVE EXAMPLE 1

An acrylic based copolymer consisting of acrylonitrile 49% by weight,vinyl chloride 50.5% by weight, and sodium styrene sulfonate 0.5% byweight was dissolved in acetone to give a resin concentration of 28% byweight, and a spinning solution having a viscosity of 4 Pa-sec wasobtained. Subsequently, the spinning solution was extruded with a nozzledraft coefficient of 0.9, using a same nozzle as in Example 1, in acoagulation bath of acetone/water having 36% by weight of acetoneconcentration, at 20 degrees C. Subsequently, a yarn obtained wasintroduced into a water-washing bath at 50 degrees C. to 60 degrees C.,and a 1.9 times of preliminary drawing was given with concurrent washingby water.

After 2.0 times of hot drawing, lost transparency was recovered bydrying under an atmosphere of wet heated wind of a dry heatingtemperature of 125 degree C., and a wet-bulb temperature of 80 degreeC., 10% of relaxation heat treatment was performed under a 145-degree C.dry heating atmosphere. Subsequently, the fiber was colored by a similarmethod as in Example 2, and a brown fiber having a single fiber size of50 dtex and an L value of 26 was obtained.

The obtained fiber had almost no uneven shape on a fiber surfacethereof, but unevenness evaluation by an optical microscope having 100times of magnification of the fiber proved to be difficult to recognizeunevenness. Moreover, this fiber had a 75% of maximum reflectance to awhite light, and optical diffusion coefficient of 0.10, and it gaveplastics-like gloss and insufficient result.

COMPARATIVE EXAMPLE 2

An acrylic based polymer consisting of acrylonitrile 49% by weight,vinyl chloride 50% by weight, and sodium styrene sulfonate 1.0% byweight was dissolved in acetone, to obtain a spinning solution with aviscosity of 4 Pa-sec by adjusting a resin concentration to 28% byweight. Subsequently, the spinning solution was extruded with a nozzledraft coefficient of 0.7, using a same nozzle as in Example 1, in acoagulation bath of acetone/water having 36% by weight of acetoneconcentration, at 20 degrees C. Then, the fiber obtained was introducedinto a water-washing bath at 50 degrees C. to 60 degrees C., and a 1.9times of-preliminary drawing was given with concurrent washing by water.

After 2.0 times of hot drawing, lost transparency was recovered bydrying under an atmosphere of wet heated wind of a dry heatingtemperature of 125 degree C., and a wet-bulb temperature of 80 degreeC., 10% of relaxation heat treatment was performed under a 145-degree C.dry heating atmosphere. Subsequently, the fiber was colored by a similarmethod as in Example 2, and a brown fiber having a single fiber size of50 dtex and an L value of 28 was obtained.

Although the obtained fiber has a surface unevenness shape, it had adifference of average height between a projected area and a depressedarea of 4 micron, and an average distance between peaks of adjacentprojected areas of 0.27 mm, showing a small uneven degree. Moreover, ithad a low optical diffusion coefficient of 0.18, and evaluation by nakedeye gave insufficient flickering gloss.

COMPARATIVE EXAMPLE 3

An acrylic based copolymer having a same composition as in Example 1 wasdissolved in acetone to give a resin concentration of 26% by weight, anda spinning solution having a viscosity of 5 Pa-sec was obtained.Subsequently, the spinning solution was extruded by a same method as inExample. 1, with a nozzle draft coefficient of 0.9, using a nozzlehaving round hole form, a pore size of 0.3 phi, and having 50 holes.Water-washing, drying, and heat treatment were performed by a similarmethod as in Example 1. Furthermore, the fiber was colored by a similarmethod as in Example 2 to obtain a brown fiber having a single fibersize of 50 dtex and an L value of 26.

The obtained fiber had almost no uneven shape on a fiber surfacethereof, but unevenness evaluation by an optical microscope having 100times of magnification of the fiber proved to be difficult to recognizeunevenness. Moreover, this fiber had a 82% of maximum reflectance to awhite light, and optical diffusion coefficient of 0.08, and it showedplastics-like gloss and gave insufficient result.

COMPARATIVE EXAMPLE 4

An acrylic based copolymer having a same composition as in Example 1 wasdissolved in acetone to give a resin concentration of 26% by weight, anda spinning solution having a viscosity of 5 Pa-sec was obtained.Subsequently, the spinning solution was extruded with a nozzle draftcoefficient of 0.9, using a same nozzle as in Example 1, in acoagulation bath of acetone/water having 36% by weight of acetoneconcentration, at 20 degrees C. Then, the fiber obtained was introducedinto a water-washing bath at 50 degrees C. to 60 degrees C., and a 1.9times of preliminary drawing was given with concurrent washing by water.

After 2.0 times of hot drawing, drying was performed under an atmosphereof wet heated wind of a dry heating temperature of 125 degree C., and awet-bulb temperature of 80 degree C., 10% of relaxation heat treatmentwas performed under a 160-degree C. dry heating atmosphere.Subsequently, the fiber was colored by a similar method as in Example 2,and a brown fiber having a single fiber size of 50 dtex and an L valueof 38 was obtained.

Inadequate recoverability of lost transparency gave an opaque fiber.Moreover, a result of evaluation of unevenness of this fiber gave adifference of average height between a projected area and a depressedarea of 2 micrometers, and an average distance between peaks of adjacentprojected areas of 0.30 mm. Moreover, maximum reflectance to a whitelight gave 28%, and an optical diffusion coefficient gave insufficientresult of 0.15.

Table 1 shows results of evaluation of reflective characteristics ofExample and Comparative Example and gloss of appearance.

TABLE 1 Uneven degree of fiber Average distance Uneven between Dryingdifference peaks of Reflective Surface Spinning conditions of averageadjacent characteristics appearance solution Nozzle Nozzle Wet-bulbheight projected L value Optical Maximum evaluation Polymer viscosityshape draft temperature [micro- areas Hue of diffusion reflectanceFlickering composition Pa-sec L/W value coefficient (degree C.) meter][mm] fiber coefficient % gloss Ex.1 AN/VD/3S 5 *-like 0.90 80 8 0.25 850.32 55 ∘ 52/46.5/1.5 shape 1.4 (white) Ex.2 AN/VD/3S 5 *-like 0.90 80 80.25 31 0.40 36 ∘ 52/46.5/1.5 shape 1.4 (brown) Ex.3 AN/VD/3S 5 *-like0.90 80 8 0.25 17 0.45 24 ∘ 52/46.5/1.5 shape 1.4 (black) Ex.4 AN/VD/3S8 *-like 0.90 80 7 0.27 35 0.36 37 ∘ 52/42/2.0 shape 1.4 (brown) Comp.AN/VD/3S 4 *-like 0.90 80 Impossible Impossible 26 0.10 75 x Ex.149/50.5/0.5 shape 1.4 to measure to measure (brown) Comp. AN/VD/3S 4*-like 0.70 80 4 0.30 28 0.18 56 Δ Ex.2 49/50/1.0 shape 1.4 (brown)Comp. AN/VD/3S 5 ◯ shape- 0.90 80 Impossible Impossible 26 0.08 82 xEx.3 52/46.5/1.5 to measure to measure (brown) Comp. AN/VD/3S 5 *-like0.90 60 2 0.30 38 0.15 28 x Ex.4 52/46.5/1.5 shape 1.4 (brown)

On one hand, Examples 1 to 4 having reflective characteristics to whitelight of a fiber (optical diffusion coefficient, maximum reflectance)within the present invention exhibit excellent flickering gloss toobservation with naked eye, and show unique gloss of appearance. On theother hand, fibers of Comparative Examples 1 to 4 out of the presentinvention have small optical diffusion coefficients, and show inadequateflickering gloss.

INDUSTRIAL APPLICABILITY

An artificial fiber for hair of the present invention is a fiber havingunique gloss of appearance and excellent designing property, whileexhibiting natural feeling of gloss, and can be broadly used forapplication as wigs, hairpieces, braids, extension hairs, and headdressfor dolls etc.

1. An artificial fiber for hair obtained from an acrylic based syntheticfiber having a single fiber size of 20 dtex to 80 dtex, the artificialfiber comprising: an optical diffusion coefficient of a fiber of notless than 0.25; a reflectance to a white light within a range of eitherof following (1) or (2), (1) a reflectance of 15% to 36% in case of afiber with an L value of less than 21 in Hunter's Lab, (2) a reflectanceof 36% to 70% in case of a fiber with an L value of not less than 21 inHunter's Lab; a knot-shaped unevenness on a surface of the artificialfiber; and a difference of average height between a projected area and adepressed area of 5 micrometers to 15 micrometers on the surface.
 2. Theartificial fiber for hair according to claim 1 further comprising adistance between peaks of adjacent projected areas in a range of 0.05 mmto 0.5 mm.
 3. The artificial fiber for hair according to claim 1,wherein the acrylic based synthetic fiber is obtained from a resincomposition having, as a principal component, a polymer consisting ofacrylonitrile 30% by weight to 85% by weight, a halogen containingmonomer 14% by weight to 69% by weight, and a hydrophilic olefin basedmonomer having sulfonic acid group 1.0% by weight to 3.0% by weight. 4.The artificial fiber for hair according to claim 2, wherein the acrylicbased synthetic fiber is obtained from a resin composition having, as aprincipal component, a polymer consisting of acrylonitrile 30% by weightto 85% by weight, a halogen containing monomer 14% by weight to 69% byweight, and a hydrophilic olefin based monomer having sulfonic acidgroup 1.0% by weight to 3.0% by weight.